Recently, it is paid attention that a hybrid vehicle is mounted with an engine and a motor generator (MG) as power sources of the hybrid vehicle in response to a social request of a low fuel consumption and a low emission. In the hybrid vehicle, since a battery is charged with a power (regeneration power) regenerated by the MG when the hybrid vehicle is decelerated, an execution time interval of an assist travel using the power of the MG and an executive time interval of an EV travel using the power of the MG can be extended, and a fuel consumption can be improved.
However, when a power regeneration is executed while the hybrid vehicle is on a long downgrade road, it is possible that a SOC indicating a remaining capacity of the battery reaches an upper limit and the battery is in a saturation state that the battery cannot be charged with the regeneration power.
According to Patent Literature 1, a deep discharge control is executed to discharge the battery to have the remaining capacity less than or equal to an intermediate region in a travel phase right before a downgrade travel phase, based on a road information obtained from a navigation device.